Hello.
I would like to implement a reed sensor to detect the opening of a door.
In order to use as less energy as possible, I would like the Arduino to power ON when the magnet is away, then transmit the data.
In other words, when the door is closed (magnet to the reed) I need the power to be broken.
Do you know how i can reverse the effect of the reed switch?
Do you advice me plug the Reed to an I/O on the Arduino rather than directly on the power?
Thanks in advance for your advices or similar experience.
Nicolas.
You can get reed switches in both normally-open and normally-closed configurations:
I would think a normally-closed switch would be a solution to your project.
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The Ruggeduino: compatible with Arduino UNO, 24V operation, all I/O's fused and protected
There is something on the arduino (and other microcontrollers) called an interrupt. Interrupts break the normal program flow and send it somewhere else-- they can get complicated. But there is a way (I'm not quite sure) to put your arduino to sleep so that it draws VERY LITTLE power. Then, when your reed switch triggers the interrupt, arduino wakes up and does whatever, goes back to sleep.